Get perfect exposure every time
Modern digital cameras are good at working out the right exposure. However, there’s no such thing as a foolproof exposure or metering system. Certain subjects can fool your camera, resulting in images that are either too light (over-exposed) or too dark (under-exposed).
For this reason, it is vital that you know which Metering mode to use in any situation so that your images look great. D-SLRs have light meters that measure the amount of light reflected back from the scene. The light sensitivity (ISO) setting will affect this.
Ultimately, the combination of aperture and shutter speed will define how your shot turns out. You can call up the histogram (tone chart) on your camera’s rear LCD screen to judge the tonal distribution of the images you take, then adjust your settings and re-shoot if necessary.
See the photography cheat sheet below where we illustrate the differences between under- corect and over-exposure, and show a histogram of each (find out how to read a histogram) so you can get a better gauge of your own camera’s histogram.
Feel free to drag and drop this infographic on to your desktop to save as a reference – and be sure to check out some of our other photography cheat sheets!
What is aperture?
Set the right combination of aperture (see our free photography cheat sheet for understanding aperture) and shutter speed and you will notice an immediate difference in your photography.
Your aperture and shutter speed combination have a big impact on your photographs. It will determine whether or not your image will be correctly exposed.
It also controls how in-focus certain areas of the image are and whether a subject is blurred or frozen. So what is aperture?
The term ‘aperture’ simply refers to a mechanical iris within a lens.
The size of this opening, or aperture, will determine the amount of light entering the lens and hitting the camera’s sensor (what digital cameras use instead of photographic film). Aperture sizes go up and down in increments and are known as f-stops.
A typical aperture range is f/2.8, f/4, f/5.6, f/8, f/11, f/16 and f/22. Just remember that the smaller the f-number, the wider the aperture. And the bigger the f-number, the narrower the aperture.
This is counter-intuitive, but you get used to it. So, a wide aperture reduces the depth of field, and a narrow aperture extends it.
What is shutter speed?
Shutter speed allows you to control the exact amount of time that the lens shutter stays open. Working in conjunction with your selected aperture, it determines the amount of light that reaches your camera’s sensor.
The main purpose of shutter speed is to determine the amount of subject movement that’s recorded. Fast shutter speeds freeze movement, while slow speeds blur it.
Shutter speeds are read in fractions of a second.
For example, 1/16 sec would capture a blurred image of a fast-moving subject, and 1/1000 sec would freeze its movement.
As mentioned, aperture and shutter speed work together. Because your control over both aperture and shutter speed affects the amount of light you let into your camera, you have to remember to maintain a correct exposure.
So, if you close the aperture by one stop (letting less light in), you need to compensate by slowing the shutter speed by one stop (to allow more light back in). This sounds complex, but your digital camera works out the correct shutter speed for you when you set the aperture, and vice versa.